摘要:

AbstractThis paper presents the results of a study of the alternating copolymerization of alkyl vinyl ethers, as electron‐donors (D), with maleonitrile and fumaronitrile, respectively, as electronacceptors (A), and a13C NMR evaluation of the stereochemistry of the copolymers. The results show that the two copolymers are stereochemically different. By use of model compounds as well as UV studies and quantum chemical (PVCILO) calculations, attempts to correlate the relationship of the complex (C) to copolymer structure have been made. We have previously reported studies on copolymerization of alkyl vinyl ethers andN‐substituted maleimides. Stereochemical consequences resulting from variation of five parameters, each of which according to Mulliken theory should vary the concentration of C relative to that of the free monomers, in every case, were that thecis‐transratio of the succinimide unit of the copolymer chain varied in accord with theory, being higher at highe

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989111

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractCyclization rate measurements were carried out on polystyrene chains of different molecular weights and labelled at both ends with 1‐pyrenyl groups, using as solvents cyclopentane (a thetasolvent), acetone (a poor solvent), and their mixtures. These mixtures exhibit a cosolvency effect for polystyrene. The results show that the rate constants for cyclization and ring‐opening are solvent‐ and chain‐length‐dependent. This was interpreted in terms of the influence of excluded volume effects on these processes. The results indicate that the solvent giving the largest excluded volume effect is an equimolar mixture of cyclopentane and acetone, which agrees with the light scattering and viscometry results for polystyrene in cyclohexane/acetone

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989112

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractCationic polymerization of 4‐tert‐butoxystyrene (1) initiated by hydrogen iodide/zinc iodide (HI/ZnI2) led to well‐defined living polymers at temperatures up to +25°C in either toluene or methylene chloride, the latter containing a small amount of tetrabutylammonium iodide (mole ratio nBu4NI/HI = 1/100). The number‐average molecular weight of the polymers increased in direct proportion to the monomer conversion, and the linear increase further continued upon addition of a second feed of1to the completely polymerized reaction mixture. Both before and after the monomer addition, the molecular weight distributions of the products were invariably very narrow (M̄w/M̄n≤ 1,1). In the polymerization in salt‐free methylene chloride, in contrast, the polymers showed broader molecular weight distributions, particularly at low conversions, and thus the presence of the ammonium salt proved mandatory for attaining living polymerization in this polar solvent. By treatment with hydrobromic acid the HI/ZnI2‐initiated poly(1) could readily be converted into poly(4‐vinylphenol) (3) that inherited the narrow molecular weight distribution and controlled molecular weigh

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989113

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractWe compare the ultimate mechanical properties and glass transition temperatures of various polyblends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and poly(dimethylsiloxane) (PDMS) including full and pseudo interpenetrating polymer networks (IPN), in which the PPO is crosslinked to different extent with both ethylenediamine and 1,6‐hexanediamine. Most of the polyblends of this system exhibit at least microphase separation with domain size varying with both composition and architecture. The full IPN's have at certain compositions a higher tensile stress to break than the crosslinked pure polymer networks. Most polyblends also exhibit multiple glass transition tempe

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989114

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractSeveral MgCl2‐supported catalysts containing different amounts of titanium and hafnium were prepared. These systems are active for the polymerization of ethylene and α‐olefins as well as for their copolymerization, giving much broader molecular weight distributions as compared with similar systems containing titanium only. Polymer properties, such as melt flow index and shear sensitivity can be varied by catalyst composition and addition of a Lewis base (ethyl benzoate). Gel permeation chromatography curves obtained in a single reactor (one‐stage process) are comparable to those obtained in two reactors (two‐stage process). An analysis of comparative kinetics for various conditions and the corresponding polymer properties suggests that Hf‐containing sites produce much longer chains than do Ti‐containing sites; at the same time Hf‐containing sites display lower activity and higher tendency to interact with ethyl benzoate. Similar investigations with model catalysts are described to support th

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989115

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractHighly syndiotactic poly(methyl methacrylate)s (PMMAs) with narrow molecular weight distribution (MWD) were prepared by polymerization of MMA in toluene at low temperatures, initiated withtert‐butyllithium (t‐C4H9Li) combined with trialkylaluminium compounds such as triethyl‐, tributyl‐, and trioctylaluminium (mole ratio Al/Li ≥ 3). Polymerization was initiated by the t‐C4H9anion and proceeded in a living manner. Several alkyl methacrylates were also polymerized with t‐C4H9Li‐(n‐C4H9)3Al to give highly syndiotactic polymethacrylates with narrow MWD. Highly syndiotactic block and random copolymers of MMA and ethyl methacrylate were obtained

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989116

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractVarious aromatic polyamides (aramids) which contain a nitro group at the amino substituted ring were synthesized and their thermal properties and degradation mechanisms were studied. Our present work showed that the nitro group in ortho position to the amide bond acts as an excellent leaving group for intramolecular nucleophilic displacement via the enol form to yield poly‐(benzoxazole)s. Thermal decomposition of ortho‐substituted aramids proceeds via a two‐stage mechanism, whereas unsubstituted aramids decompose in one step. The first step represents the loss of HNO2and the second step is due to degradation of the resulting benzoxazole polymer. Model compound and high‐temperature FT‐IR studies of these materials also give supportive evidences for the cyclization

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989117

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA comprehensive analysis of the charge‐transfer (CT) complex crystallization in the reticulate doping process is presented. Our description enables to distinguish the main parameters controlling the CT complex crystallization conditions indispensable for obtaining highly conductive systems. The discussion concerns the role of the following parameters: temperature, solubility of the CT complex, solvent evaporation rate, initial thickness of the solution layer, polymer concentration, and the ratio of the mass of the CT complex to the mass of the polymer in the solution. The presented discussion of the influence of these parameters of the CT complex crystallization process is in good accordance with our studies of obtaining various conducting polymer/CT complex systems. The factors mentioned above have a strong hold on the morphology and the content of the crystalline CT complex, and hence on the electrical properties of reticulate doped system

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989118

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY